1. Field of the Invention
The present invention relates to an actuator and in particular to an actuator having a buffer structure.
2. Description of Related Art
The actuators have been commonly used in automatic hospital beds, treadmills, and wheelchairs for adjusting the position and elevation thereof. In particular, during the first aid treatment for patients, the use of a fast mechanism for releasing the actuator fast can adjust the hospital bed to obtain the most precious rescue time. However, during the fast release of the actuator, the impact force caused by fast falling may injure the patient. Therefore, how to provide a buffer function before the end of the fast falling becomes an important topic associated with the present invention.
The traditional actuator comprises an electric motor, a transmission mechanism, and a fast release mechanism. The electric motor has a worm shaft. The transmission mechanism comprises a drive screw and a worm gear sleeved around the drive screw and engaged with the worm shaft. The fast release mechanism comprises two cylindrical connecting parts; one is fixed to and rotated with the drive screw; the other is fixed to and rotated with the worm gear. A torque transmission member is disposed at each corresponding end of the cylindrical connecting parts. By means of the clutch between the two cylindrical connecting parts, the drive screw and the worm gear can rotate together or separately.
However, the traditional actuator in operation presents the following problems. Without the structure of the buffer mechanism, the impact force caused by fast falling may injure the patient during the fast release of the actuator. To solve this problem, a pneumatic cylinder is usually installed beside the actuator to provide a buffer function. However, the addition of the pneumatic cylinder will make the hospital bed a more complex structure and increase the manufacturing cost. The present invention provides such an actuator having a buffer structure without the additional pneumatic cylinder, which makes the hospital bed simple and decreases the manufacturing cost.